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There are trains travelling on 4 parallel tracks. The frequencies of [#permalink]
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24 Jun 2013, 11:41
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There are trains travelling on 4 parallel tracks. The frequencies of trains traveling on these tracks at equal interval of time are 4, 6, 8, 12 per hour respectively. If all trains start at 7 AM, after how much time will all the trains start together from the same place? A. 1 Hour B. 12 Hours C. 24 Hours D. 1/2 hours E. 1/4 Hours
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Re: There are trains travelling on 4 parallel tracks. The frequencies of [#permalink]
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24 Jun 2013, 13:30
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guerrero25 wrote: There are trains travelling on 4 parallel tracks. The frequencies of trains traveling on these tracks at equal interval of time are 4, 6, 8, 12 per hour respectively. If all trains start at 7 AM, after how much time will all the trains start together from the same place?
A. 1 Hour B. 12 Hours C. 24 Hours D. 1/2 hours E. 1/4 Hours hi 1st track frequency is 4 trains/hr= every 15 min 1 train will leave 2nd track frequency is 6 trains/ hr = every 10 min 1 train will leave 3rd track frequency is 8 trains/hr= every 7.5 min 1 train will leave 4th track frequency is 12 trains /hr= every 5 min 1 train will leave the time when each track train will leave at same time next time will be X mins (after 7 am)= =>where X=LCM of (15/10/7.5/5)=30 mins=1/2 hrs. hence D. KUDOS If it helped
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Re: There are trains travelling on 4 parallel tracks. The frequencies of [#permalink]
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08 Aug 2013, 11:50
There are trains traveling on 4 parallel tracks. The frequencies of trains traveling on these tracks at equal interval of time are 4, 6, 8, 12 per hour respectively. If all trains start at 7 AM, after how much time will all the trains start together from the same place?
This is, more or less, a question regarding lowest common multiples. The LCM of 15, 10, 7.5 and 5 is 30.
4 train every 15 minutes 6 train every 10 minutes 8 train every 7.5 minutes 12 train every 5 minutes
ANSWER: D. 1/2 hours



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Re: There are trains travelling on 4 parallel tracks. The frequencies of [#permalink]
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08 Aug 2013, 12:07
guerrero25 wrote: There are trains travelling on 4 parallel tracks. The frequencies of trains traveling on these tracks at equal interval of time are 4, 6, 8, 12 per hour respectively. If all trains start at 7 AM, after how much time will all the trains start together from the same place?
A. 1 Hour B. 12 Hours C. 24 Hours D. 1/2 hours E. 1/4 Hours .................. after leaving, the schedule(min) of 2nd train for 4lines= 15min 10min 7.5min 5min LCM = 30 mins . so 1/2 hour(D) Answer
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Re: There are trains travelling on 4 parallel tracks. The frequencies of [#permalink]
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19 Nov 2013, 23:19
Quote: 15min 10min 7.5min 5min LCM = 30 mins . so 1/2 hour(D) Answer Can anyone please explain how to get the LCM. I am trying but i am getting 150. 15, 10, 75/10, 5 LCM of 15,10,75,5 and HCF of 1,1,10,1 = 150/1 Thanks & Regards Vinni



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Re: There are trains travelling on 4 parallel tracks. The frequencies of [#permalink]
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22 Nov 2013, 09:13
vinnik wrote: Quote: 15min 10min 7.5min 5min LCM = 30 mins . so 1/2 hour(D) Answer Can anyone please explain how to get the LCM. I am trying but i am getting 150. 15, 10, 75/10, 5 LCM of 15,10,75,5 and HCF of 1,1,10,1 = 150/1 Thanks & Regards Vinni Please help on this one. I will really appreciate. How to get LCM as 30. I am getting 150. Please Vinni



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Re: There are trains travelling on 4 parallel tracks. The frequencies of [#permalink]
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13 Dec 2013, 06:16
vinnik wrote: vinnik wrote: Quote: 15min 10min 7.5min 5min LCM = 30 mins . so 1/2 hour(D) Answer Can anyone please explain how to get the LCM. I am trying but i am getting 150. 15, 10, 75/10, 5 LCM of 15,10,75,5 and HCF of 1,1,10,1 = 150/1 Thanks & Regards Vinni Please help on this one. I will really appreciate. How to get LCM as 30. I am getting 150. Please Vinni Hi, You have to reduce the fraction 75/10 into its lowest term, i.e 15/2 LCM of 15,10,15,5 and HCF of 1,1,2,1 = 30/1 LCM = 30 Hope that helps..



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Re: There are trains travelling on 4 parallel tracks. The frequencies of [#permalink]
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13 Dec 2013, 20:02
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vinnik wrote: vinnik wrote: Quote: 15min 10min 7.5min 5min LCM = 30 mins . so 1/2 hour(D) Answer Can anyone please explain how to get the LCM. I am trying but i am getting 150. 15, 10, 75/10, 5 LCM of 15,10,75,5 and HCF of 1,1,10,1 = 150/1 Thanks & Regards Vinni Please help on this one. I will really appreciate. How to get LCM as 30. I am getting 150. Please Vinni I found following approach to be much simpler for calculating LCM which involves a decimal number : LCM(15,10,7.5,5)  multiply the decimal number by 10 (it is done to take decimal out of the picture) and subsequently multiply other numbers as well with 10. So, now what you are left with is to find LCM (150,100,75,50) , which comes to be 300. Now divide 300 with the 10 you multiplied your original number set with and that will give you your original LCM, which is 30. Hope you find it useful.
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Re: There are trains travelling on 4 parallel tracks. The frequencies of [#permalink]
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06 May 2017, 08:49
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Re: There are trains travelling on 4 parallel tracks. The frequencies of [#permalink]
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06 May 2017, 11:31
1/4, 1/6,1/8,1/12 hour per train lcm of 1/4, 1/6,1/8,1/12=1/2 ans:D




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